The Dog Who Knew Superman - S2-E9
Other mistake: A gangster pushes a dog into a well and the dog can be heard splashing around. The man's wife is furious and several people are unable to retrieve the dog. Superman tunnels into the ground and into the bottom of the well and emerges holding the dog. Both he and the dog are completely dry.
Dave and the Teenager - S11-E17
Other mistake: When the Harris family moves into an apartment across the hall from David and June Nelson, their 14-year-old daughter, Betty, develops a crush on David. When David and June step out onto their outdoor patio, they see Betty watching them from her own patio. This could not be possible.